1. Field of the Invention
The invention relates generally to automatic clothes dryers. In one aspect, the invention relates to a method of introducing heat for drying clothes in a clothes dryer comprising controlling the output of a dryer heating system based on an airflow rate through the dryer airflow system. In another aspect, the invention relates to an automatic clothes dryer having a controller for controlling operation of the dryer heating system relative to an airflow rate through the dryer airflow system.
2. Description of the Related Art
Automatic clothes dryers are well known, and typically comprise a cabinet enclosing a horizontally rotating drum accessible through an access door at the front of the cabinet for holding clothing items to be dried. An electric heater is frequently utilized and is positioned in an air inlet assembly upstream of the drum for heating the drying air prior to its entry into the drum. The drying air is delivered to the drum through a motor-driven blower assembly.
The temperature to which the air must be heated is dependent upon several factors, such as the fabric type being dried, the degree of dryness desired, the airflow through the dryer drum, and the size of the dryer load. Control of the air temperature typically involves controlling the operation of the heater and, thus, the electric power delivered to the heater. When the air temperature must be increased, the heater is turned on. When the air temperature must be decreased, the heater is turned off.
Traditional clothes dryers use thermostats to cycle a single heater element on and off. However, thermostats are capable of only two operating modes; i.e. full on or full off. Thus, the power delivered to the heater cycles between a preselected full power value and zero power. However, cycling between full power and zero power is an inefficient use of power, can contribute to increased drying times, can be hard on heater components, and does not provide satisfactory control for many fabric types and airflow conditions.